A general 6-speed manual transmission (hereinafter referred to as a transmission) will be described with reference to FIG. 8.
A transmission TM includes an input shaft 10, an output shaft 11, and a counter shaft 12. The output shaft 11 is disposed coaxially with this input shaft 10. The counter shaft 12 is disposed parallel to the input shaft 10 and output shaft 11. An input main gear 13 is disposed on the input shaft 10. A 1st speed (1st) main gear M1, a 2nd speed (2nd) main gear M2, a 3rd speed (3rd) main gear M3, a 4th speed (4th) main gear M4, and a reverse main gear MR are journally supported on the output shaft 11, and a 6th speed (6th) main gear M6 is fixedly secured on the output shaft 11. On the counter shaft 12, an input counter gear 14, a 1st speed counter gear C1, a 2nd speed counter gear C2, a 3rd speed counter gear C3, a 4th speed counter gear C4, and a reverse counter gear CR are fixedly secured, and a 6th speed counter gear C6 is journally supported. The input counter gear 14 engages with the input main gear 13. The 1st speed counter gear C1 engages with the 1st speed main gear M1. The 2nd speed counter gear C2 engages with the 2nd speed main gear M2. The 3rd speed counter gear C3 engages with the 3rd speed main gear M3. The 4th speed counter gear C4 engages with the 4th speed main gear M4. The reverse counter gear CR engages with the reverse main gear MR via an idle gear IR. The 6th speed counter gear C6 engages with the 6th speed main gear M6.
In this transmission TM, a sleeve S1 is spline-engaged (meshed) with a hub 111 secured to the output shaft 11. When the sleeve S1 is spline-engaged with a dog DR of the reverse main gear MR, the output shaft 11 rotates reversely. When the sleeve S1 is spline-engaged with a dog D1 of the 1st speed main gear M1, the output shaft 11 rotates at a speed corresponding to the 1st speed. A sleeve S2 is spline-engaged with a hub H2 secured to the output shaft 11. When the sleeve S2 is spline-engaged with a dog D2 of the 2nd speed main gear M2, the output shaft 11 rotates at a speed corresponding to the 2nd speed. When the sleeve S2 is spline-engaged with a dog D3 of the 3rd speed main gear M3, the output shaft 11 rotates at a speed corresponding to the 3rd speed.
A sleeve S4 is spline-engaged with a hub 114 secured to the output shaft 11. When the sleeve S4 is spline-engaged (meshed) with a dog D4 of the 4th speed main gear M4, the output shaft 11 rotates at a speed corresponding to the 4th speed. When the sleeve S4 is spline-engaged with a dog D5 of the input main gear 13, the output shaft 11 rotates at a speed corresponding to the 5th speed (5th) (in the directly-coupled state). A sleeve S6 is spline-engaged with a hub H6 secured to the counter shaft 12. When the sleeve S6 is spline-engaged with a dog D6 of the 6th speed counter gear C6, the output shaft 11 rotates at a speed corresponding to the 6th speed.
The sleeves S1, S2, S4, and S6 are manually operated by a driver with a driver's shift lever within the driver's cabin via shift forks F1, F2, F4, and F6 and a shift shaft.
A shift control system in an actual transmission will be described with reference to FIG. 9 and FIG. 10.
In FIG. 9 and FIG. 10, a low speed shift shaft 15a and a high speed shift shaft 15b are disposed parallel to the vehicle width direction and along the longitudinal direction of the vehicle. At a rear portion of the low speed shift shaft 15a, a first shift fork F1 is fixedly secured. The first shift fork F1 shifts between the 1st speed and the reverse (Rev). In front of the first shift fork F1, a second shift fork F2 is disposed to be movable with respect to the shift shaft 15a. The second shift fork F2 shifts between the 2nd speed and the 3rd speed.
On the other hand, a third shift fork F4 is disposed at a front portion of the high speed shift shaft 15b such that the third shift fork F4 is movable with respect to the shift shaft 15b. The third shift fork F4 shifts between the 4th speed and the 5th speed. At the rear portion of the shift shaft 15b, a counter shaft shift 15c is disposed parallel to the shift shaft 15b. The shift shaft 15b and the counter shaft shift 15c are coupled together by a link lever 16. On this counter shaft shift 15c, a fourth shift fork F6 is fixedly secured. The fourth shift fork F6 shifts to the 6th speed.
On the low speed shift shaft 15a, a boss 17a is disposed in front of the second shift fork F2. A reverse-1st speed shift block B1 is integral with the boss 17a. On the high speed shift shaft 15b, a boss 17b is disposed behind the third shift fork F4. A 6th speed shift block B6 is integral with the boss 17b. 
Between the reverse-1st speed shift block B1 and the 6th speed shift block B6, a 2nd speed-3rd speed shift block B2 and a 4th speed-5th speed shift block B4 are arranged. The 2nd speed-3rd speed shift block B2 is coupled to the second shift fork F2 by a coupling member 18a. The 4th speed-5th speed shift block B4 is coupled to the third shift fork F4 by a coupling member 18b. 
The reverse-1st speed shift block B1, the 2nd speed-3rd speed shift block B2, the 4th speed-5th speed shift block B4, and the 6th speed shift block B6 are arranged from the low speed gear to the high speed gear. With the operation of the driver's shift lever, select operations are sequentially performed from the neutral position of the reverse-1st speed to those of the 2nd speed-3rd speed, the 4th speed-5th speed, and the 6th speed. Subsequently, a shift operation is performed from the neutral position of the selected shift block B1, B2, B4, or B6 to a desired gear position (shift position).
That is, when the shift lever engages with the reverse-1st speed shift block B1, the reverse-1st speed shift block B1 is moved forward by the shift lever. Accordingly, the first shift fork F1 is moved forward via the boss 17a and the shift shaft 15a so as to shift from the neutral position to the 1st speed. When the reverse-1st speed shift block B1 is moved rearward, the first shift fork F1 is moved rearward so as to shift from the neutral position to the reverse gear position.
When switching to the 2nd speed or the 3rd speed is desired, the engagement position of the shift lever is moved to the neutral position of the 2nd speed-3rd speed shift block B2 by the select operation. From this state, the 2nd speed-3rd speed shift block B2 is moved rearward by the shift lever. Accordingly, the second shift fork F2 is moved rearward via the coupling member 18a so as to shift from the neutral position to the 2nd speed. The 2nd speed-3rd speed shift block B2 is moved forward so as to shift from the neutral position to the 3rd speed.
When switching to the 4th speed or the 5th speed is desired, the shift lever is moved to the neutral position of the 4th speed-5th speed shift block B4 by the select operation. Subsequently, the 4th speed-5th speed shift block B4 is moved rearward. Accordingly, the third shift fork F4 is moved rearward via the coupling member 18b so as to shift from the neutral position to the 4th speed. The 4th speed-5th speed shift block B4 is moved forward so as to shift from the neutral position to the 5th speed.
When switching to the 6th speed is desired, the shift lever is moved to the neutral position of the 6th speed shift block B6 by the select operation. Subsequently, the 6th speed shift block B6 is moved rearward. Accordingly, the shift shaft 15b is moved rearward via the boss 17b, and the counter shaft shift 15c is moved forward via the link lever 16. Thus, the fourth shift fork F6 is moved forward so as to shift from the neutral position to the 6th speed.
In FIG. 9 and FIG. 10, reference numeral 19 denotes ball clicks for holding the shafts 15a and 15b at the respective gear positions and neutral positions.
FIG. 11(a) illustrates the above-described shift patterns of the transmission TM.
In FIG. 11(a), the reverse-1st speed shift block B1 described with reference to FIG. 9 and FIG. 10 is used to perform a shift operation between the reverse and the 1st speed (shift operation to the reverse or to the 1st speed). The 2nd speed-3rd speed shift block B2 is used to perform a shift operation between the 2nd speed and the 3rd speed (shift operation to the 2nd speed or to the 3rd speed). The 4th speed-5th speed shift block B4 is used to perform a shift operation between the 4th speed and the 5th speed (shift operation to the 4th speed or to the 5th speed). The 6th speed shift block B6 is used to perform a shift operation to the 6th speed. When the shift lever is moved by the select operation, the shift lever is moved along the aligned neutral positions of the reverse-1st speed shift block B1, the 2nd speed-3rd speed shift block B2, the 4th speed-5th speed shift block B4, and the 6th speed shift block B6.
A gear shifting operation with this manual transmission will be described. For example, in the case from the 2nd speed to the 3rd speed, as illustrated in FIG. 11(b), the gear is disengaged from the 2nd speed to the neutral position. Subsequently, the gear is engaged from the neutral position to the 3rd speed. This is straight shifting (i.e., shifting without the select operation). As illustrated in FIG. 11(c), in the case of a gear shift operation from the 3rd speed to the 4th speed, the gear is disengaged from the 3rd speed to the neutral position. Subsequently, a select operation is performed on the shift lever so as to move to the neutral position of the 4th speed-5th speed shift block B4, and the gear is engaged from the neutral position to the 4th speed. This is an elbow plus elbow (crank) shifting (i.e., shifting with the select operation).
Operations similar to the above-described operations are required in an automatic transmission that is equipped with an automatic shifting device prepared based on the transmission illustrated in FIG. 9 and FIG. 10.
That is, it is necessary to provide shift levers to be selectively engaged with the reverse-1st speed shift block B1, the 2nd speed-3rd speed shift block B2, the 4th speed-5th speed shift block B4, and the 6th speed shift block B6. The shift levers are driven by actuators such as motors to move the shift blocks B1, B2, B4, and B6.
In the case where the shift operation is performed with the actuators, the rotation speed of the engine and the rotation speed of the output shaft are detected by rotation sensors in the transmission TM described with reference to FIG. 8. The detection results are introduced to an engine control unit (ECU). Based on a gear shift map (speed change map) stored in the ECU, a drive control is performed on the actuator associated with the appropriate (desired) gear position to achieve the desired gear shifting.